Technical Field
The present disclosure relates to a sensing signal analysis method and a system thereof. More particularly, the present disclosure relates to a gas cross-sensitivity effect analysis method and a system thereof.
Description of Related Art
Acid rains, depletion of ozone and photochemical smog, produced by NOX, SOX, and other volatile organic compounds, have constituted enormous threat to human health and ecological environment. The emission of SOX and other volatile organic compounds have been substantially reduced by the improved oil refinery techniques. Therefore, the removal of NOX from waste gases has already become one of the most important tasks of environmental pollution treatment in the 21st century.
Using urea solution as a reductant, selective catalyst reduction (SCR) is one of the most effective aftertreatment systems for reducing engine exhaust NOx emission. The NGK/Continental Smart NOx Sensor (SNS) is widely used for exhaust aftertreatment systems such as SCR. The output signal of the SNS, however, is characterized with different levels of oscillation as the urea injection changes. Moreover, due to the cross-sensitivity of the SNS to the ammonia concentration for higher-than-stoichiometric ammonia injection, the sensor signal cannot be interpreted in a straight-forward way as it is not clear whether excess NOX or NH3 is present. So that it not only causing the logic errors of the SCR aftertreatment systems and the excess ammonia injection causing wasteful, but also the contaminants produced by excess ammonia and SOX causing reduced the efficiency of the SCR aftertreatment systems.
Prior arts attempt to solve this problem of gas cross-sensitivity of the SCR aftertreatment systems. As is known, one is placed two SNS on upstream and downstream of the SCR aftertreatment systems to determine the ammonia concentration excess or not. Another is installed a chemiluminescence analyzer to calculate the ammonia concentration. As mention above, prior arts need to install another SNS or apparatus, increase not only cost but also system weight and complication.